具有setTimeout關閉，變量訪問的自我調用功能

Question

我如何獲得setTimeout中的a_var？someFunction？

謝謝。

function someFunction(){ 
      (function why(){ 
         setTimeout(function(){ 

          var a_var='help I wanna get out!'; 
         return a_var;//<-useless? 

         }, 25); 
        })(); 
     }; 

Answer 1

你有更高的範圍申報a_var，就像這樣：

var a_var = 'I can help from here'; 
function someFunction(){ 
    setTimeout(function(){ 
    a_var = "help I wanna get out!"; 
    }, 25); 
} 
someFunction(); 
console.log(a_var); // logs 'I can help from here' 
setTimeout(function(){ 
    console.log(a_var); 
}, 30); // logs 'help I wanna get out!';